A multiple chamber type semiconductor manufacturing system is constructed as shown in FIG. 1 of the drawings attached hereto and has a plurality of process chamber stations 2a, 2b, 2c, 2d and 2e disposed around a transfer chamber 1 and also has arranged therein a pair of workpiece delivery stations 3 by each of which the workpiece is delivered to an outside thereof, and in which the space within the transfer chamber 1 is kept in an evacuated state by a suction unit.
And, the above mentioned transfer chamber 1 is constructed as shown in FIG. 2 of the drawings attached hereto and has a handling robot A provided at a central region thereof so as to be rotatable. It also is provided with a plurality of partition walls 5 that serve as the peripheral walls thereof with each wall opposing to each of the said stations 2a, 2b, 2c, 2d and 2e and the said workpiece delivery stations 3 and in which there are also provided a plurality of gates 56 each of which constitutes both an inlet and an outlet for the workpiece to be fed into and out of each of the said stations. Each such gate 6 is configured so as to be opened and closed by an opening and closing door (not shown) that is disposed in opposition to each of the said gates 6.
As the above mentioned handling robot A, there has hitherto been used an apparatus of so called flog leg type with a pair of arms and its construction is as shown in FIGS. 3 to 7 of the drawings attached hereto.
In this construction, the said pair of arms, designated at 7a and 7b, of an identical length are arranged so as to be rotatable about a center of rotation. On the other hand, there are provided a pair of transfer tables 8a and 8b that have their respective bases, to each of which is connected one end of each of two legs of each of a pair of links 9a and 9b of an identical length, respectively. The said one end of each of the said two legs of each of the both links 9a and 9b is coupled via a flog leg type transfer table attitude regulating mechanism to each of the said transfer tables 8a and 8b, respectively, so that the said links 9a and 9b may be rotated in a pair of directions each of which is completely symmetrical with respect to the said transfer tables 8a and 8b.
And, one of the pair of links 9a and 9b which are coupled to the said transfer tables 8a and 8b is coupled to one of the said pair of arms 7a and 7b whereas the other of the said links 9a and 9b is coupled to the other of the said arms 7a and 7b, respectively.
FIG. 4A in the drawings attached hereto shows the said transfer table attitude regulating mechanism B of the above mentioned flog leg type, in which the respective forward end portions of the said links 9a and 9b in the pair which are coupled to the said transfer tables 8a and 8b are coupled together in a gear configuration that comprises a pair of gears 9c and 9c which mesh with each other so that the angles of attitude .theta. R and .theta. L of the said links 9a and 9b with respect to the said transfer tables 8a and 8b may always be identical to each other. This allows each of the said transfer tables 8a and 8b to be always oriented in a radial direction and operated in the radial direction.
It should be noted, however, that the above mentioned links 8a and 9b may not necessarily be coupled together in a gear arrangement, but may alternatively be coupled together with a crossed belting arrangement 9a as shown in FIG. 4B of the drawings attached hereto.
FIG. 5 of the drawings attached hereto shows a mechanism for permitting the above mentioned arms 7a and 7b to be rotated independently of each other.
The respective bases of said arms 7a and 7b are each configured in the form of a ring shaped boss and such ring shaped bosses 10a and 10b are configured so as to be coaxial about the said center of rotation and to be rotatably supported with respect to a frame 1a of the said transfer chamber 1.
On the other hand, the said ring shaped bosses 10a and 10b have a pair of disk shaped bosses 11a and 11b disposed therein, respectively, wherein a said ring shaped boss and a said disk shaped boss are opposing to each other and arranged so as to be coaxial with each other. A first pair of said mutually opposing ring shaped and disk shaped bosses and a pair of the said mutually opposing ring shaped and disk shaped bosses are coupled and decoupled with each other via each of magnetic couplings 12a and 12b, respectively, in each of the directions of rotation.
The above mentioned pair of the disk shaped bosses 11a and 11b have their respective rotary shafts 13a and 13b which are arranged so as to be coaxial with each other. The said rotary shafts 13a and 13b are coupled to the output sections of a pair of motor units 14a and 14b, respectively, which are coaxial with the said frame 1a of the transfer chamber 1 and are supported with their positions deviated in their axial direction.
The above mentioned motor units 14a and 14b have each integrally coupled thereto a motor 15 which comprises, for example, an AC servo motor and a speed reduction gear 16 which comprises, for example, a Harmonic Drive (trade name, identically referred to hereinafter). Such reduction gears 16 and 16 have their output sections which are coupled to the respective bases of the said rotary shafts 13a and 13b, respectively.
Since the space within the said transfer chamber 1 in which the arms 7a and 7b are positioned is held in an evacuated state, there is provided a sealing partition 17 each between the said ring shaped boss 10a and the said disk shaped boss 11a and between the said ring shaped boss 10b and the said disk shaped boss 11b of the present arm rotary mechanism.
FIGS. 7A and 7B show an operation of the above mentioned handling robot A. As shown in FIG. 7A, when the said two arms 7a and 7b are located at a pair of diametrically symmetrical positions, respectively, with respect to the said center of rotation, the said links 9a and 9b will be in a state in which they assume their most expanded positions with respect to each of the said transfer tables 8a and 8b so that the latter may both be displaced toward the said center of rotation.
In this state, by rotating the said two arms 7a and 7b in an identical direction, it can be seen that the said two transfer table 8a and 8b will be rotated about the said center of rotation whilst maintaining the radial positions thereof.
Also, by rotating the said two arms 7a and 7b in the directions in which they may approach towards each other (or in the mutually opposite directions), from the state shown in FIG. 7A, it can be seen that one of the said transfer tables 8a that is located at such a position that the angle made by the said two arms 7a and 7b is reduced will be pushed by the said links 9a and 9b so as to be projected in its radially outward direction so that it may be thrusted into one of the above mentioned stations 2a, 2b, 2c, 2d, 2e and 3 which are disposed adjacent to the radially outward side with respect to the said transfer chamber 1 as shown in FIG. 7B.
At this point of time, whilst the other of the said transfer tables will be displaced towards the said center of rotation, it can be seen that its amount of displacement will be small because of an angle that is made between the said arms 7a and 7b and an angle that is made between the said links 9a and 9b.
The above mentioned conventional handling robot has been expected to provide a functional effect as a two arm robot by virtue of the advantage that a pair of transfer tables are provided and can alternately or consecutively be used for each of a variety of stations. It has been found, however, that as a matter of reality there arises the following problem
More specifically, since each of the said pair of the transfer tables is coupled via a pair of links commonly to a pair of arms, respectively, it has been found that when one transfer table is displaced towards a station, the other transfer table must necessarily be in a stand-by state and that this will make it impossible for an individual transfer table to be displaced optionally towards a station.
Also, in a case where a transfer table is to be rotated, a pair of transfer tables must be rotated together and this makes it impossible for an individual transfer table to be rotated as desired.
From the reasons mentioned above, in spite of the fact that there have specially been provided a pair of transfer tables, it is found that such a provision itself almost has not contributed to a desired shortening of the time cycle in a semiconductor manufacturing system that has been provided with a plurality of process chambers around a transfer chamber.
Also, in the above mentioned conventional handling robot, it is noted that a drive mechanism for rotating each of the said arms is constituted with a pair of the said motor units 14a and 14b, each of which combines the said motor 14 with a said speed reduction gear 16 that is high in the ratio of speed reduction. Since such speed reduction gears 16 and 16 of the said motor units 14a and 14b have their output sections which are connected via a pair of the said rotary shafts to a pair of the said disk shaped bosses 11a and 11b, it has been found that there must be an elongated path of power transmission provided from each of the respective output sections of the said speed reduction gears to a corresponding one of the said disk shaped bosses.
It may also be noted that although as shown in FIG. 6 of the drawing attached hereto there has been another construction of the handling robot in which a pair of disk shaped bosses 11a' and 11b' are provided interiorly with a pair of inner teeth gears 11c and 11d, respectively, with which a pair of pinion gears 13c and 13d mesh, respectively, that are securely fixed to a pair of rotary shafts 13a' and 13b' which in turn are coupled to the speed reduction gears of the said motor units 14a and 14b, respectively, such a construction again requires that there should be provided an elongated path of power transmission from each of the respective output sections of the said speed reduction gears to a corresponding one of the said disk shaped bosses.
In the drive mechanism of the conventional handling robot, the need for an elongated path of power transmission from a motor unit to a disk shaped boss as noted above has resulted in an insufficiently low torsional rigidity. Also, since a transmission torque is increased at a speed reduction gear that is remote from a disk shaped boss via a rotary shaft, a deformation thereof may give rise to an error in rotation thereof which as it is produces an error in rotary angle of an arm, thus having constituted a bottle neck in accurately controlling the rotary angle of the handling robot in the prior art.
It may also be noted that a handling robot to be used in a clean room or an evacuated state in an above mentioned semiconductor manufacturing system requires that a dust should be introduced therein at a very minimum so that no foreign matter may adhere to an object being conveyed.
In a conventional handling robot as generally mentioned above and particularly as shown in FIG. 8 of the drawings attached hereto, in which a transfer table 8 that enters into and comes out of each of the said stations 2a-2e via a said gate 6 is coupled to a pair of the said arms 7a and 7b via the said transfer table attitude regulating mechanism B of a flog leg type having a pair of rotary nodes, however, it has been found that there arises the problem that a portion of a gear transmission mechanism or a belt transmission mechanism which is included to constitute the said transfer table attitude regulating mechanism B may be a source of dusts from which a dust can develop. A further problem has been that such a portion also tends to be loosened, giving rise to a positioning inaccuracy.
Accordingly, the present invention has been made with the foregoing problems taken into account, and has for its generic object to provide a handling robot whereby the cycle time for a manufacturing operation can be shortened by permitting an action for conveying each of a plurality of transfer tables into and out of each of the stations and an action thereof to be carried out independently of each other as desired whereas the accuracy at which an arm is controlledly rotated can be enhanced by permitting any error within the path of power transmission not to influence the control of the rotary angle of the said arm.
A further important object of the present invention is to provide a handling robot whereby a dust that may be produced at a coupling portion between a transfer table and an arm can be reduced at a very minimum and any loosening that may develop at the said portion can also be reduced at a very minimum.